Mandibular symphyseal separation in dogs and cats usually occurs secondary to trauma. Typically these include being hit by car, falling from a height, fighting another dog or cat, or some form of blunt force trauma.1
Patients with mandibular separation may hold their mouth slightly open, have noticeable wounds, and may struggle to prehense food. Frequently canine patients will attempt to eat once they have recovered from any concurrent injuries the trauma may have caused.
Feline patients are often less willing to eat while the mandible remains unstable, although in minimally displaced mandibular symphyseal separation they sometimes will be able to.
Examination and diagnosis
Careful examination and palpation of the mandible may require sedation or even general anesthesia to reduce the risk of the examiner being inadvertently bitten. Placing a finger on each lower canine crown and applying alternating downward pressure will allow diagnosis of mandibular symphyseal separation.
Any patient with a mandibular injury should be assessed for signs of head trauma, including assessment of neurological function and checked for signs of raised intracranial pressure. The patient should also be assessed for other more life threatening injuries that may have been incurred from the trauma such as pneumo- or haemothorax, haemoabdomen, and urinary tract rupture.
If a mandibular separation is diagnosed or strongly suspected, then imaging of the mandible is indicated to further assess the area to check for other possible fractures and to allow assessment of the teeth.1 Radiographs can be sufficient for assessment of fractures of the horizontal ramus of the mandible however for full assessment of the vertical ramus and condylar process a computed tomography (CT) scan is usually required.1 Dental film can be useful for closer assessment of teeth suspected to be involved in any fractures.
The majority of mandibular symphyseal separations can be treated with a circumferential stainless-steel wire placed immediately caudal to the canine teeth. The technique has been well described.2,3
A large gauge needle with an inner diameter wide enough to fit the desired size of wire is used to guide passage of the wire (Figure 1). Wire twisters are required for securing the circumferential wire. The twists then need to be cut, leaving at least two full and secure twists in the patient. The skin incision on the ventral mandible can be closed with a cruciate skin suture.
Alternatively, if the incision is small it can be left open and granulation tissue will tend to form around the wire. Most patients tolerate the wire extremely well and if they have no other major injuries, I expect them to start eating soft food within 24 to 48 hours.
An Elizabethan collar is advised for the duration of wire placement, although most patients do not seem to try to interfere with the wire. Soft food should be fed while the wire is in place. The aim is for fibrous tissue to form between the mandibular rami to restore the union between them. This typically takes around six to eight weeks, at which point the wire can be removed.
Further, a general anesthetic is recommended to allow safe wire removal. An alternative technique places the wire twists to the side of one of the canine teeth with acrylic covering the twists to prevent abrasion to the mucosa.3 This may make removal slightly easier.
Following wire removal soft food should continue to be fed for a couple of weeks before the patient is gradually transitioned back to their normal diet. Complications are infrequent and most commonly involve dehiscence and/or discharge from the ventral mandible incision.
In occasional cases, the canine teeth are not present, such as in the patient seen in Figure 2. In these cases any injury to the mucosa should be sutured and then the patient should be restricted to a soft food diet for six to eight weeks. It is important to remind owners to remove any chews or toys the patient could have access to. In this case, a fibrous union between the mandibular rami formed without the requirement for surgical intervention and the patient had an excellent functional outcome.
Jessica McCarthy, BVSc, ECVS, currently works at Auburn University as Assistant Professor of Small Animal Orthopedics. She has recently become a diplomate of the European College of Veterinary Surgeons. Dr. McCarthy attended Bristol University for her veterinary degree and spent two years in general practice in England after graduating. On her path to specialization, she completed a small animal rotating internship at the University of Cambridge, an orthopedic internship at Liverpool University and her residency at the University of Edinburgh. She has a particular interest in elbow disease both developmental and traumatic. McCarthy is passionate about ensuring everyone in the veterinary profession can work in a diverse and inclusive atmosphere.
Faolain Barrett, DVM, a surgical resident at University of Wisconsin, Madison, contributed to this article.
- Johnston SA, Tobias KM. Veterinary Surgery: Small Animal Expert Consult-E-Book. Elsevier Health Sciences; 2017.
- Glyde M, Lidbetter D. Management of fractures of the mandible in small animals. In Pract. 2003 Nov;25(10):570–85.
- Mulherin BL, Snyder CJ, Soukup JW. An alternative symphyseal wiring technique. J Vet Dent. 2012;29(3):176–84.